﻿/*
* Copyright (c) 2010-2012 Tesla Engine Group
* 
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* 
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* 
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

using System.Collections.Generic;

namespace Tesla.Collections {
    /// <summary>
    /// A List that manages its own read-only version of itself, rather than
    /// creating a new one each time AsReadOnly() is called. The read-only
    /// version is only created when first requested, and uses the existing data
    /// to read from.
    /// 
    /// This is useful if you want the functionality of a List, but be able to
    /// limit to read-only outside of its manager/owner.
    /// </summary>
    /// <typeparam name="T">Type of data</typeparam>
    public sealed class TeslaList<T> : List<T> {

        private ReadOnlyList<T> _readOnlyList;

        /// <summary>
        /// Creates a new instance of <see cref="TeslaList&lt;T&gt;"/>.
        /// </summary>
        public TeslaList() : base() { }

        /// <summary>
        /// Creates a new instance of <see cref="TeslaList&lt;T&gt;"/>.
        /// </summary>
        /// <param name="capacity">The initial list capacity.</param>
        public TeslaList(int capacity) : base(capacity) { }

        /// <summary>
        /// Creates a new instance of <see cref="TeslaList&lt;T&gt;"/>.
        /// </summary>
        /// <param name="collection">An enumerable collection to create the list from.</param>
        public TeslaList(IEnumerable<T> collection) : base(collection) { }

        /// <summary>
        /// Returns a read-only copy of this list. 
        /// </summary>
        /// <returns>Read only list</returns>
        public new ReadOnlyList<T> AsReadOnly() {
            if(_readOnlyList == null) {
                _readOnlyList = new ReadOnlyList<T>(this);
            }
            return _readOnlyList;
        }
    }
}
